1. Field of the Invention
The present invention relates to a process for the preparation of unsaturated polyesters from particular glycols and acids or anhydrides which comprise tetrahydrophthalic anhydride and/or acid, adapted to the preparation of unsaturated polyester resins which, after cross-linking, rapidly loose their surface tackiness, and which are adapted to the production of materials having high flexibility and resistance to creasing. The resins are further particularly adapted to make, by the addition of suitable fillers, putties that can be applied by spraying and/or by smearing with a putty knife. The present invention further refers to the unsaturated polyesters and the unsaturated polyester resins obtained by the aforesaid method, as well as to the aforesaid putties made from polyester resin and suitable fillers.
2. Prior Art
It is known that the oxygen in the air has an inhibiting effect on the cross-linking reaction, which occurs with a radicalic mechanism in the hardening of unsaturated polyester resins. The phenomenon is more or less accentuated depending on the type of resin. For many unsaturated polyester resins, the phenomenon has the consequence that a certain residual tackiness remains on the surface which is exposed to the air during the hardening and persists even after a long time. It is known to include certain additives in the unsaturated polyesters in an attempt to avoid such drawback. The use of such additives however causes other drawbacks, such as e.g. the inadequate adhesion of the finish varnishes.